Contamination-preventing agent composition and contamination preventing method

ABSTRACT

To provide a contamination-preventing agent composition and a contamination preventing method which even if the composition is imparted only to a dryer on the upstream side, a sufficient amount of the composition can be imparted to a dryer on the downstream side via a wet paper, and pitch contamination of a plurality of dryers can be prevented sufficiently as a whole. 
     The present invention is a contamination-preventing agent composition imparted to dryers D 1  to D 8  in a dry part D of a paper machine and comprising an emulsion, a re-transfer agent and water, wherein the re-transfer agent has a cloud point of 55° C. or higher and an HLB value of 8 to 15, and preferably a contamination-preventing agent composition wherein the dynamic surface tension value at a lifetime of 100 ms by a maximum bubble pressure method is 65 mN/m or less.

TECHNICAL FIELD

The present invention relates to a contamination-preventing agentcomposition and a contamination preventing method, and more particularlyto a contamination-preventing agent composition and a contaminationpreventing method capable of preventing pitch contamination of aplurality of dryers in a dry part of a paper machine.

BACKGROUND ART

A paper making process in a paper machine generally has a wire part inwhich a liquid in which pulp is dispersed in water is placed on a mesh(wire) for papermaking and excess water is naturally dropped to obtain awet paper, a press part for transferring moisture in the wet paper to afelt by passing the wet paper between a pair of press rolls and pressingit by the press rolls via the felt, thereby dewatering the wet paper, adry part for drying the paper by contacting the wet paper which haspassed through the press part with a plurality of heated driers, toobtain a paper, and a reel part for winding the paper on a bar called aspool.

In the above-mentioned dry part, there is a problem that the pitchsticks to the surface of a dryer. If the pitch sticks to the dryer, awet paper is contaminated, and the yield thereof is significantlyreduced.

On the other hand, a silicone-based contamination-preventing agentcomposition and a non-silicone contamination-preventing agentcomposition are known as a contamination-preventing agent compositionfor preventing pitch contamination in a dry part of a paper makingprocess.

For example, as the silicone-based contamination-preventing agentcomposition, a contamination-preventing agent composition containing apolysiloxane compound having a predetermined chemical structural formulaand having from 0.5 to 5 amino-modified groups per molecule of thepolysiloxane compound is known (see, e.g., Patent Document 1).

Further, as the non-silicone contamination-preventing agent composition,a contamination-preventing agent composition containing a non-siliconeoil and an emulsifier for emulsifying the non-silicone oil, wherein theemulsifier is a neutralized product of a fatty acid and an aminecompound is known (see, e.g., Patent Document 2).

However, with these contamination-preventing agent compositions,although it is possible to prevent the pitch contamination of a dryer onthe upstream side to which the contamination-preventing agentcomposition is imparted, it is impossible to sufficiently prevent thepitch contamination of a dryer on the downstream side only by itself.For this reason, it is necessary to impart a contamination-preventingagent composition to each of a plurality of dryers.

In the present specification, “dryer on the upstream side” means a dryerpositioned upstream with respect to traveling of a wet paper, and “dryeron the downstream side” means a dryer positioned downstream with respectto traveling of a wet paper.

In contrast, there is known a contamination-preventing agent compositioncontaining a low molecular polysiloxane compound having a predeterminedchemical structural formula and a polymer polysiloxane compound having apredetermined chemical structural formula, wherein the kinematicviscosity of the low molecular polysiloxane compound at 25° C. is 10 to300 mm²/s, the kinematic viscosity of the polymer polysiloxane compoundat 25° C. is 40 to 90,000 mm²/s, the number of modified groups permolecule of the low molecular polysiloxane compound is from 0.1 to 3.0,the number of modified groups per molecule of the polymer polysiloxanecompound is 1.0 to 10, and the repeating number m of the polysiloxaneunit in the low molecular polysiloxane compound and the repeating numbern of the polysiloxane unit in the polymer polysiloxane compound satisfythe relationship of 2 m≤n (see, e.g., Patent Document 3).

In such a contamination-preventing agent composition, the polymerpolysiloxane compound forms a coating film on a dryer on the upstreamside, while the low molecular polysiloxane compound transfers to a wetpaper and is carried by the wet paper, and the low-molecularpolysiloxane compound is re-transferred to a dryer on the downstreamside to which the wet paper is guided, hence, pitch contamination of aplurality of dryers can be prevented as a whole.

CITATION LIST Patent Literature

PTL 1: Japanese Patent No. 4868628

PTL 2: Japanese Patent No. 4828001

PTL 3: Japanese Patent No. 4868629

SUMMARY OF INVENTION Technical Problem

However, with the contamination-preventing agent composition in theabove Patent Document 3, it is possible to prevent pitch contaminationof a plurality of dryers as a whole, but particularly in a dryer on thedownstream side, it cannot be said that pitch contamination can besufficiently prevented.

That is, with the contamination-preventing agent composition in theabove Patent Document 3, the polymer polysiloxane compound to form acoating film is not transferred to the wet paper, and only the lowmolecular polysiloxane compound is transferred to the wet paper, hence,there is a disadvantage that the amount of re-transfer to the wet paper(hereinafter referred to as “pick-up amount.”) is small, and sufficientamount cannot be imparted to a dryer on the downstream side.

In addition, since the coating film composed of the low-molecularpolysiloxane compound is extremely weak and easily re-transferred, thereis also a disadvantage that even if it is imparted to a dryer on thedownstream side, it is re-transferred again and it is hard to remain onthe dryer.

The present invention has been made in view of the above circumstances,and has an object of providing a contamination-preventing agentcomposition and a contamination preventing method which even if thecomposition is imparted only to a dryer on the upstream side, asufficient amount of the composition can be imparted to a dryer on thedownstream side via a wet paper, and pitch contamination of a pluralityof dryers can be prevented sufficiently as a whole.

Solution to Problems

The present inventors have intensively studied to solve theabove-described problem and resultantly found that the above-describedproblem can be solved by allowing the contamination-preventing agentcomposition to have a constitution containing a re-transfer agent havingpredetermined physical properties, leading to completion of the presentinvention.

The present invention is (1) a contamination-preventing agentcomposition imparted to a dryer in a dry part of a paper machine andcomprising an emulsion, a re-transfer agent and water, wherein there-transfer agent has a cloud point of 55° C. or higher and an HLB valueof 8 to 15.

The present invention is (2) the contamination-preventing agentcomposition according to (1), wherein the dynamic surface tension valueat a lifetime of 100 ms by a maximum bubble pressure method is 65 mN/mor less.

The present invention is (3) the contamination-preventing agentcomposition according to (1) or (2), wherein the dryer is made of castiron, and the contact angle to the cast iron is 70° or less.

The present invention is (4) the contamination-preventing agentcomposition according to any one of (1) to (3), wherein the re-transferagent is at least one selected from the group consisting ofpolyoxyalkylene alkyl ether, polyoxyalkylene fatty acid ester,polyoxyalkylene sorbitan fatty acid ester and polyoxyalkylene sorbitolfatty acid ester.

The present invention is (5) the contamination-preventing agentcomposition according to any one of (1) to (4), wherein the emulsion iscomposed of a non-silicone oil, water and an emulsifier, and thenon-silicone oil is at least one selected from the group consisting ofpolybutenes, synthetic ester oils, mineral oils, vegetable oils andliquid paraffins.

The present invention is (6) the contamination-preventing agentcomposition according to (5), wherein the compounding ratio of there-transfer agent with respect to 10% by mass of the non-silicone oil is0.1% by mass to 10% by mass.

The present invention is (7) the contamination-preventing agentcomposition according to any one of (1) to (6), wherein the compoundingratio of the re-transfer agent is 0.01% by mass to 10% by mass.

The present invention is (8) the contamination-preventing agentcomposition according to any one of (1) to (7), wherein a coating filmis formed by being imparted to the dryer, and a part of the coating filmis re-emulsified when the coating film comes in contact with a wetpaper.

The present invention is (9) a contamination preventing method,comprising a first step of imparting the contamination-preventing agentcomposition according to any one of claims (1) to (7) to a dryer on theupstream side to form a coating film, a second step of bringing a wetpaper into contact with the coating film to re-emulsify a part of thecoating film and transfer the re-emulsified emulsion to the wet paper,and a third step of bringing the wet paper carrying the emulsion intocontact with a dryer on the downstream side to impart the emulsion tothe downstream dryer.

Advantageous Effects of Invention

With the contamination-preventing agent composition of the presentinvention, moisture is removed by drying of the emulsion to form acoating film, and then a moisture-containing wet paper comes intocontact with the film, whereby a part of the coating film isre-emulsified.

At this time, since the coating film contains a re-transfer agent forpromoting re-transfer, the re-emulsified contamination-preventing agentcomposition will promptly re-transfer to the wet paper.

Here, by using a re-transfer agent having a cloud point of 55° C. orhigher, when the contamination-preventing agent composition containing are-transfer agent forms a coating film on a dryer, re-transfer of thecontamination-preventing agent composition to the wet paper can bepromoted without losing the active performance of the re-transfer agenteven during heating with the dryer. The temperature of the dryer isgenerally 55° C. or higher.

By using a re-transfer agent having an HLB value of 8 to 15, it ispossible to effectively activate the interface between water and thecoating film and promote re-emulsification.

It is preferable that the compounding ratio of the re-transfer agent is0.01% by mass to 10% by mass based on the total amount.

For these reasons, by using a re-transfer agent having a cloud point of55° C. or higher and an HLB value of 8-15, the pick-up amount of theemulsion obtained by re-emulsification of the coating film onto the wetpaper can be improved.

Therefore, for example, if a contamination-preventing agent compositionis given to a dryer at the most upstream side with respect to travelingof the wet paper, it is possible to impart a sufficient amount even to adryer on the downstream side via the wet paper.

As a result, it is possible to prevent pitch contamination as a wholefor a plurality of dryers.

For the contamination-preventing agent composition of the presentinvention, the speed of movement to the interface between the coatingfilm and the wet paper can be made faster by setting the dynamic surfacetension value at a lifetime of 100 ms according to the maximum bubblepressure method to 65 mN/m or less.

That is, in the paper machine, it is a very short time from imparting ofthe contamination-preventing agent composition to a dryer until thedryer comes into contact with a wet paper, and by setting the dynamicsurface tension value within the above range, it becomes possible topromptly exert the function of the re-transfer agent of re-emulsifyingthe coating film.

In the contamination-preventing agent composition of the presentinvention, the dryer is made of cast iron, and the contact angle to thecast iron is 70° or less, accordingly, the emulsion easily forms acoating film along the surface of the drier.

In the contamination-preventing agent composition of the presentinvention, the effect of re-emulsification can be exerted surely whenthe re-transfer agent is at least one selected from the group consistingof polyoxyalkylene alkyl ether, polyoxyalkylene fatty acid ester,polyoxyalkylene sorbitan fatty acid ester and polyoxyalkylene sorbitolfatty acid ester.

In the contamination-preventing agent composition of the presentinvention, when the emulsion is composed of a non-silicone oil, waterand an emulsifier, the compounding ratio of the re-transfer agent withrespect to 10% by mass of the non-silicone oil is 0.1% by mass to 10% bymass.

When the non-silicone oil is at least one selected from the groupconsisting of polybutenes, synthetic ester oils, mineral oils, vegetableoils and liquid paraffins, a coating film can be easily formed on thedryer, re-emulsification is easily performed, and pitch contaminationcan be surely prevented.

In the case where the contamination-preventing agent composition of thepresent invention forms a coating film by being imparted to a dryer anda part of the coating film is re-emulsified with a re-transfer agent bycontact of the coating film with a wet paper, even if the composition isimparted only to a dryer on the upstream side, a sufficient amount ofthe composition can be imparted to a dryer on the downstream side viathe wet paper, and pitch contamination of a plurality of dryers can beprevented sufficiently as a whole.

In the contamination preventing method of the present invention, pitchcontamination of a plurality of dryers can be prevented sufficiently asa whole via a first step, a second step and a third step by using thecontamination-preventing agent composition described above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a flowchart showing a contamination preventing method using acontamination-preventing agent composition according to the presentembodiment.

FIG. 2 is an explanatory diagram for explaining a contaminationpreventing method according to the present embodiment.

FIG. 3 is a schematic diagram showing a dryer using acontamination-preventing agent composition according to the presentembodiment.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the drawings as necessary. Thepositional relationship such as up, down, left and right are based onthe positional relationship shown in the drawing unless otherwise noted.Further, the dimensional ratios of the drawings are not limited to theillustrated ratios.

The contamination-preventing agent composition according to the presentembodiment can prevent pitch contamination of a dryer by being impartedto the dryer in a dry part of a paper machine.

Specifically, even if the composition is imparted only to a dryer on theupstream side, a sufficient amount can be imparted to a dryer on thedownstream side via a wet paper. As a result, pitch contamination can besufficiently prevented for a plurality of dryers as a whole.

With the contamination-preventing agent composition, a coating film isformed by being imparted to a drier, thereby preventing pitchcontamination of the dryer.

Thereafter, when the coating film comes into contact with the wet paper,a part of the coating film is re-emulsified, and thecontamination-preventing agent composition is transferred to the wetpaper.

The transferred contamination-preventing agent composition is carried bythe wet paper and is imparted also to a dryer on the downstream side.

Details of these will be described later.

As a result, according to the contamination-preventing agent compositionof the present embodiment, it is possible to sufficiently prevent pitchcontamination as a whole for a plurality of dryers.

It is preferable for the contamination-preventing agent composition thatthe dynamic surface tension value at a lifetime of 100 ms by a maximumbubble pressure method is 65 mN/m or less.

When the dynamic surface tension value of the contamination-preventingagent composition exceeds 65 mN/m, the speed at which the re-transferagent moves to the interface between the dryer and the emulsion tends tobe delayed as compared with the case where the dynamic surface tensionvalue is within the above range. In this case, emulsification does notoccur instantaneously, and the pick-up amount to the wet paper becomesinsufficient.

The dynamic surface tension value is a value measured in an environmentof 25° C. using an automatic dynamic surface tension meter BP-D5(manufactured by Kyowa Interface Science, Inc.).

It is preferable for the contamination-preventing agent composition thatthe contact angle to cast iron is 70° or less.

When the contact angle of the contamination-preventing agent compositionto cast iron exceeds 70°, there are drawbacks that it takes more time toremove moisture by drying and it becomes difficult to form a uniformcoating as compared with the case where the contact angle is within theabove range.

The contact angle is a value measured in an environment of 25° C. and50% humidity using DropMaster DMs-401, Teflon needle 18 G.

Here, the dryer is generally made of cast iron.

Therefore, when the contamination-preventing agent composition isimparted to a dryer, the contamination-preventing agent composition canform a coating film on the surface of the dryer instantaneously bysetting the contact angle to cast iron within the above-described range.

Cast iron is formed by casting an alloy containing iron as a maincomponent and containing at least one selected from the group consistingof nickel, chromium, carbon and silicon.

The cast iron used to measure the contact angle may be the same as ordifferent from the cast iron of a dryer. It is preferable that both ofthem are cast irons having a ten-point average roughness (Rz) of 0.16 μmor less, a maximum height (Rmax) of 0.21 μm or less, and an arithmeticmean roughness (Ra) of 0.04 μm or less.

In the contamination-preventing agent composition according to thepresent embodiment, the emulsion is composed of a non-silicone oil,water and an emulsifier. That is, the non-silicone oil is emulsifiedwith an emulsifier using water as a medium.

The non-silicone oils includes mineral oils such as gear oil, dryer oil,turbine oil, spindle oil and the like, vegetable oils such as coconutoil, linseed oil, castor oil, rapeseed oil, corn oil and the like,liquid paraffin, isoparaffin, polyisobutylene, polybutene, maleatedpolybutene, synthetic ester oil, polyethylene wax, micro wax,12-hydroxystearic acid and the like. These may be used singly or incombination of two or more.

Among them, the non-silicone oil is preferably at least one selectedfrom the group consisting of polybutenes, synthetic ester oils, mineraloils, vegetable oils and liquid paraffins from the viewpoint of a filmforming property and a pitch contamination preventing property.

The emulsifier is not particularly limited, and known nonionicsurfactants, anionic surfactants, cationic surfactants, amphotericsurfactants and the like are used.

Among these, the emulsifier is preferably an anionic surfactant or anonionic surfactant, from the viewpoint of storage stability of theemulsion.

In the contamination-preventing agent composition according to thepresent embodiment, the re-transfer agent includes polyoxyalkylene alkylethers, polyoxyalkylene alkyl thioethers, polyoxyalkylene fatty acidesters, polyoxyalkylene sorbitan fatty acid esters, polyoxyalkylenesorbitol fatty acid esters, glycerin mono-fatty acid esters and thelike. These may be used singly or in combination of two or more.

Among them, the re-transfer agent is preferably at least one selectedfrom the group consisting of polyoxyalkylene alkyl ethers,polyoxyalkylene fatty acid esters, polyoxyalkylene sorbitan fatty acidesters and polyoxyalkylene sorbitol fatty acid esters, from theviewpoint of ease of re-emulsification.

The re-transfer agent preferably has a cloud point of 55° C. or higher.When the cloud point is lower than 55° C., the function as a re-transferagent may possibly be lost due to heat of a dryer as compared with thecase where the cloud point is within the above range.

When the re-transfer agent is water-soluble, the cloud point is atemperature at which an aqueous solution containing 1% by mass of there-transfer agent is heated to become cloudy.

In contrast, when the re-transfer agent is water-insoluble, the cloudpoint is a temperature at which a 25% (w/w) diethylene glycol monobutylether aqueous solution containing 10% by mass of the re-transfer agentis heated to become cloudy.

The re-transfer agent preferably has an HLB value of 8 to 15.

When the HLB value is less than 8 or exceeds 15, it is impossible tosufficiently activate the interface between the coating film made of thenon-silicone oil described above and water, as compared with the casewhere the HLB value is within the above range.

The HLB value is a value measured by a known Griffin method.

In the contamination-preventing agent composition, the compounding ratioof the re-transfer agent is preferably 0.01% by mass to 10% by mass withrespect to the total amount of the contamination-preventing agentcomposition.

When the compounding ratio of the re-transfer agent with respect to thetotal amount of the contamination-preventing agent composition is lessthan 0.01% by mass, there is a fear that the re-transfer becomesinsufficient and the pick-up amount to the paper decreases, as comparedwith the case where the compounding ratio of the re-transfer agent iswithin the above range, while when the compounding ratio of there-transfer agent with respect to the total amount of thecontamination-preventing agent composition exceeds 10% by mass, there-transfer agent itself bonds to the pitch or the like, which may causecontamination, as compared with the case where the compounding ratio ofthe re-transfer agent is within the above range.

In the contamination-preventing agent composition, the compounding ratioof the re-transfer agent with respect to 10% by mass of the non-siliconeoil is preferably 0.1% by mass to 10% by mass.

When the compounding ratio of the re-transfer agent with respect to 10%by mass of the non-silicone oil is less than 0.1% by mass, there is afear that the re-transfer agent cannot sufficiently re-transfer thenon-silicone oil, as compared with the case where the compounding ratioof the re-transfer agent is within the above range, while when thecompounding ratio of the re-transfer agent with respect to 10% by massof the non-silicone oil exceeds 10% by mass, there is a fear that theeffect of preventing adhesion of pitch contamination by the non-siliconeoil becomes insufficient, as compared with the case where thecompounding ratio of the re-transfer agent is within the above range.

The contamination-preventing agent composition according to the presentembodiment is produced by stirring and mixing a non-silicone oil, anemulsifier and water to obtain an emulsion and stirring and mixing theemulsion, a re-transfer agent and water.

In the above-described stirring and mixing, a hand mixer, a homogenizerand the like are suitably used. In addition, they may be dispersed by adispersing machine such as a sand mill, a bead mill, a ball mill or thelike.

Next, the contamination preventing method using the above-mentionedcontamination-preventing agent composition will be described.

FIG. 1 is a flowchart showing a contamination preventing method usingthe contamination-preventing agent composition according to the presentembodiment.

As shown in FIG. 1, the contamination preventing method according to thepresent embodiment has a first step S1 of imparting thecontamination-preventing agent composition a dryer on the upstream sideto form a coating film, a second step S2 of bringing a wet paper intocontact with the coating film to re-emulsify a part of the coating filmand transfer the re-emulsified emulsion to the wet paper, and a thirdstep S3 of bringing the wet paper carrying the emulsion into contactwith a dryer on the downstream side to impart the emulsion to thedownstream dryer.

FIG. 2 is an explanatory diagram for explaining a contaminationpreventing method according to the present embodiment.

As shown in FIG. 2, in the contamination preventing method, thecontamination-preventing agent composition is first directly imparted toa dryer 10 on the upstream side of a dry part in the first step S1.

At this time, the dryer 10 is at a high temperature in order to dry awet paper W. For this reason, in the surface of the dryer 10, a part ofwater contained in the contamination-preventing agent composition isevaporated, and a coating film 1 is formed of a non-silicone oil. Thecoating film 1 contains also a re-transfer agent.

Then, in the second step S2, when the traveling wet paper W comes intocontact with a dryer 10 on the upstream side, at the same time as thewet paper W is dried, a part of the coating film 1 on the surface of thedryer 10 is re-emulsified by water contained in the wet paper W. At thistime, since the re-transfer agent is contained in the emulsion 1 a ofthe re-emulsified contamination-preventing agent composition, theemulsion 1 a is transferred to the wet paper W.

The time from imparting the contamination-preventing agent compositionto a dryer until the wet paper comes into contact with the dryer isextremely short, and is 40 ms to 160 ms.

Next, in the third step S3, the wet paper W travels while holding theemulsion 1 a and comes into contact with a dryer 11 on the downstreamside.

Then, since the side of the wet paper W to which the emulsion 1 a hasbeen transferred comes into contact with the dryer 11 on the downstreamside, a part of the emulsion 1 a is re-transferred to the dryer 11 onthe downstream side.

Then, by separation of the wet paper W, the re-transferred emulsion 1 ais heated again by the dryer 11 on the downstream side to form a coatingfilm.

On the other hand, the emulsion 1 a which has not been re-transferred tothe dryer 11 on the downstream side is transferred to a dryer on thefurther downstream side of by the wet paper W, and re-transferred to thedryer in a like manner.

By repeating the imparting of the emulsion 1 a of thecontamination-preventing agent composition to a dryer on the downstreamside as described above, it becomes possible to impart the emulsion 1 aof the contamination-preventing agent composition to a plurality ofdryers.

In the contamination preventing method, a contamination-preventing agentcomposition is continuously imparted to a dryer 10 on the upstream side,so that an emulsion of the contamination-preventing agent composition isimparted continuously also to a drier 11 on the downstream side via thewet paper W.

In the contamination preventing method according to the presentembodiment, since the contamination-preventing agent compositiondescribed above is used, it is possible to increase the pick-up amountof the contamination-preventing agent composition to the wet paper W.

Further, through the first step S1, the second step S2 and the thirdstep S3 described above, it is possible to prevent pitch contaminationas a whole for the plurality of dryers.

Next, the spraying position of the contamination-preventing agentcomposition according to the present embodiment will be described.

FIG. 3 is a schematic diagram showing a dryer using thecontamination-preventing agent composition according to the presentembodiment.

As shown in FIG. 3, the contamination-preventing agent composition isused in a dry part D.

The dry part D includes a wet paper W, a plurality of cylindrical dryersD1, D2, D3, D4, D5, D6, D7 and D8 (hereinafter referred to as “D1 toD8”) for heating and drying the wet paper W, canvases K1, K2 forpressing the wet paper against the dryers D1 through D8, a canvas rollKR for guiding the canvases K1, K2, a breaker stack roll B for gentlyadjusting the smoothness and paper thickness of the dried wet paper W,and a calender roll C for adjusting the smoothness and paper thicknessof the dried wet paper W.

In the dry part D, the wet paper W is pressed against the surfaces ofthe dryers D1 to D8 by the canvases K1 and K2. As a result, the wetpaper W adheres to the dryers D1 to D8 and is simultaneously heated anddried.

Thereafter, the wet paper W is sandwiched by the breaker stack roll B,and then the wet paper W is densified by the calender roll C.

The contamination-preventing agent composition is imparted to the dryerD 1 on the most upstream side of the dry part D at the position of thearrow A.

The method of imparting the contamination-preventing agent compositionis not particularly limited, and for example, a shower method using aspray nozzle or the like, a spray method, and the like are used.

After the contamination-preventing agent composition is imparted at theposition of the arrow A of the dryer D 1, the dryer D 1 is rotated toguide the wet paper W and the emulsion of the contamination-preventingagent composition is transferred to the wet paper W.

Then, the emulsion of the contamination-preventing agent composition iscarried by the wet paper W and re-transferred to a dryer D3 on thedownstream side to which the wet paper is guided, and re-transferred toa dryer D5 on the further downstream side and re-transferred to a dryerD7 on the further downstream side.

On the other hand, the contamination-preventing agent compositionimparted at the position of the arrow A of the dryer D2 is re-transfersto a dryer D4 on the downstream side to which the wet paper is guided,and re-transferred to a dryer D6 on the further downstream side andre-transferred to a dryer D8 on the further downstream side.

By repeating the re-transfer as described above, thecontamination-preventing agent composition or the emulsion thereof isimparted to the dryers D1 to D8 as a whole and pitch contamination canbe prevented.

At this time, the spray amount of the contamination-preventing agentcomposition is preferably 0.02 mg/m² to 2.0 mg/m² in terms of thenonvolatile component amount per passage area of the wet paper.

When the spray amount is less than 0.02 mg/m², thecontamination-preventing agent composition does not sufficiently adhereto the surface of a dryer and pitch contamination cannot be sufficientlyprevented in some cases, as compared with the case where the sprayamount is within the above-described range. In contrast, when the sprayamount is over 2.0 mg/m², there is a possibility that thecontamination-preventing agent composition itself causes contamination,as compared with the case where the spray amount is within theabove-described range.

Although preferred embodiments of the present invention have beendescribed above, the present invention is not limited to theabove-described embodiments.

The contamination-preventing agent composition according to the presentembodiment is composed of an emulsion, a re-transfer agent and water,and may contain additives such as a chelating agent, a pH adjustingagent, a preservative, a dispersing agent, a viscosity adjusting agent,a solid lubricant, a wetting agent, a dusting-preventing agent, arelease agent, an adhesive, a surface modification agent, a cleaningagent, a paper strength enhancer, a sizing agent, a retention aid, awater repellent, an oil repellent, an anti-lubricant, a softener and thelike.

According to the present embodiment, the contamination-preventing agentcomposition is imparted to a dryer, but it may be imparted not only to adryer but also to a canvas, a canvas roll, a calender roll, a breakerstack roll and the like.

In the contamination-preventing agent composition according to thepresent embodiment, the dryer is made of cast iron, but it may be madeof another material.

EXAMPLES

Hereinafter, the present invention will be described more specificallybased on Examples and Comparative Examples, but the present invention isnot limited to the following Examples.

Example 1

To an emulsion containing 10 parts by mass of liquid paraffin(non-silicone oil), 0.1 part by mass of polycarboxylic acid amine(emulsifier, anionic surfactant), 0.1 part by mass of stearic acid amine(emulsifier, anionic surfactant) and 88.8 parts by mass of purifiedwater was added 1.0 part by mass of polyoxyalkylene alkyl ether(re-transfer agent, cloud point: 62° C., HLB: 8.1) and they were mixedby stirring to prepare a sample A of a contamination-preventing agentcomposition.

The dynamic surface tension value at 100 ms of the sample A was 45 mN/mand the contact angle to cast iron was 50°.

Example 2

A sample B of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 1.0 part by mass ofanother polyoxyalkylene alkyl ether (re-transfer agent, cloud point: 79°C., HLB: 14.7) was used instead of the polyoxyalkylene alkyl ether.

The dynamic surface tension value at 100 ms of the sample B was 49 mN/mand the contact angle to cast iron was 54°.

Example 3

A sample C of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 1.0 part by mass ofpolyoxyalkylene sorbitan fatty acid ester (re-transfer agent, cloudpoint: 60° C. or higher, HLB: 14.9) was used instead of thepolyoxyalkylene alkyl ether.

The dynamic surface tension value at 100 ms of the sample C was 62 mN/mand the contact angle to cast iron was 68°.

Example 4

A sample D of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 10 parts by mass ofcastor oil (vegetable oil, non-silicone oil) was used instead of liquidparaffin.

The dynamic surface tension value at 100 ms of the sample D was 52 mN/mand the contact angle to cast iron was 60°.

Example 5

A sample E of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 10 parts by mass ofcastor oil (vegetable oil, non-silicone oil) was used instead of liquidparaffin and 1 part by mass of polyoxyalkylene fatty acid ester(re-transfer agent, cloud point: 60° C. or higher, HLB: 13.6) was usedinstead of the polyoxyalkylene alkyl ether.

The dynamic surface tension value at 100 ms of the sample E was 43 mN/mand the contact angle to cast iron was 52°.

Example 6

A sample F of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 10 parts by mass of estersynthetic oil (non-silicone oil) was used instead of liquid paraffin.

The dynamic surface tension value at 100 ms of the sample F was 50 mN/mand the contact angle to cast iron was 62°.

Example 7

A sample G of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 10 parts by mass of estersynthetic oil (non-silicone oil) was used instead of liquid paraffin and1 part by mass of polyoxyalkylene sorbitol fatty acid ester (re-transferagent, cloud point: 80° C. or higher, HLB: 13.8) was used instead of thepolyoxyalkylene alkyl ether.

The dynamic surface tension value at 100 ms of the sample G was 42 mN/mand the contact angle to cast iron was 50°.

Comparative Example 1

A sample H of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that the polyoxyalkylene alkylether was not used.

The dynamic surface tension value at 100 ms of the sample H was 72 mN/mand the contact angle to cast iron was 102°.

Comparative Example 2

A sample I of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 1.0 part by mass ofanother polyoxyalkylene alkyl ether (cloud point: 53° C., HLB: 6.5) wasused instead of the polyoxyalkylene alkyl ether.

The dynamic surface tension value at 100 ms of the sample I was 66 mN/mand the contact angle to cast iron was 85°.

Comparative Example 3

A sample J of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 1.0 part by mass ofanother polyoxyalkylene alkyl ether (cloud point: 52° C., HLB: 8.0) wasused instead of the polyoxyalkylene alkyl ether.

The dynamic surface tension value at 100 ms of the sample J was 66 mN/mand the contact angle to cast iron was 76°.

Comparative Example 4

A sample K of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 1.0 part by mass ofanother polyoxyalkylene alkyl ether (cloud point: 62° C., HLB: 7.8) wasused instead of the polyoxyalkylene alkyl ether.

The dynamic surface tension value at 100 ms of the sample K was 66 mN/mand the contact angle to cast iron was 79°.

Comparative Example 5

A sample L of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 1.0 part by mass ofanother polyoxyalkylene alkyl ether (cloud point: 100° C. or higher,HLB: 16.0) was used instead of the polyoxyalkylene alkyl ether.

The dynamic surface tension value at 100 ms of the sample L was 67 mN/mand the contact angle to cast iron was 85°.

Comparative Example 6

A sample M of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 10 parts by mass ofcastor oil (vegetable oil, non-silicone oil) was used instead of liquidparaffin and the polyoxyalkylene alkyl ether was not used.

The dynamic surface tension value at 100 ms of the sample M was 69 mN/mand the contact angle to cast iron was 82°.

Comparative Example 7

A sample N of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 10 parts by mass ofcastor oil (vegetable oil, non-silicone oil) was used instead of liquidparaffin and 1.0 part by mass of another polyoxyalkylene alkyl ester(cloud point: 53° C., HLB: 6.5) was used instead of the polyoxyalkylenealkyl ether.

The dynamic surface tension value at 100 ms of the sample N was 68 mN/mand the contact angle to cast iron was 78°.

Comparative Example 8

A sample O of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 10 parts by mass ofcastor oil (vegetable oil, non-silicone oil) was used instead of liquidparaffin and 1.0 part by mass of another polyoxyalkylene alkyl ester(cloud point: 100° C. or higher, HLB: 16.0) was used instead of thepolyoxyalkylene alkyl ether.

The dynamic surface tension value at 100 ms of the sample O was 68 mN/mand the contact angle to cast iron was 80°.

Comparative Example 9

A sample P of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 10 parts by mass of estersynthetic oil (non-silicone oil) was used instead of liquid paraffin andthe polyoxyalkylene alkyl ether was not used.

The dynamic surface tension value at 100 ms of the sample P was 70 mN/mand the contact angle to cast iron was 90°.

Comparative Example 10

A sample Q of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 10 parts by mass of estersynthetic oil (non-silicone oil) was used instead of liquid paraffin and1.0 part by mass of another polyoxyalkylene alkyl ester (cloud point:53° C., HLB: 6.5) was used instead of the polyoxyalkylene alkyl ether.

The dynamic surface tension value at 100 ms of the sample Q was 66 mN/mand the contact angle to cast iron was 73°.

Comparative Example 11

A sample R of a contamination-preventing agent composition was preparedin the same manner as in Example 1 except that 10 parts by mass of estersynthetic oil (non-silicone oil) was used instead of liquid paraffin and1.0 part by mass of another polyoxyalkylene alkyl ester (cloud point:100° C. or higher, HLB: 16.0) was used instead of the polyoxyalkylenealkyl ether.

The dynamic surface tension value at 100 ms of the sample R was 67 mN/mand the contact angle to cast iron was 75°.

(Evaluation Method) 1. Contamination Preventing Test

Each 0.2 g of the samples obtained in Examples 1 to 7 and ComparativeExamples 1 to 11 were sprayed onto a 5×25 cm square stainless steelplate and dried with heating at 80° C.

Next, a 5×25 cm square broad-leaf tree bleached kraft pulp (LBKP) wasadjusted to a water content of 60%, which was brought into contact withthe sample on the stainless steel plate for 10 seconds at a contactpressure of 30 g/cm². In this way, a part of the sample was transferredto LBKP.

Next, another stainless steel plate was prepared, and theabove-mentioned LBKP was brought into contact with this at a contactpressure of 30 g/cm² for 10 seconds, and the sample was re-transferredfrom the LBKP to the another stainless steel plate.

Then, onto the another stainless steel plate, a heat-resistant tape(trade name: No. 5413, manufactured by 3M Japan Co., Ltd.) was pasted soas to sandwich the re-transferred sample, and the sample was heated at80° C.

Then, the magnitude of the force when peeling the heat-resistant tapewas measured. The smaller the value, the easier the pitch is peeled(pitch is hard to adhere), meaning the high contamination preventingeffect. As a blank, measurements were also made on samples not sprayedon the stainless steel plate.

The obtained results are shown in Table 1.

2. Actual Machine Evaluation

The samples of Examples 1, 5 and 7 and Comparative Examples 1, 2, 5, 6,7, 9 and 10 were sprayed at a rate of 5 cc/min to the dryer D1 at theposition of the arrow A shown in FIG. 3, and the dryer was operated for60 minutes.

Further, doctor blades (dryer contamination-removing apparatus) notshown were placed so as to come into contact with the dryers D1, D3, D5and D7, respectively.

For each dryer, the presence or absence of the pitch accumulated on thedoctor blade was visually observed.

The obtained results are shown in Table 1.

TABLE 1 Peeling force Presence or absence of pitch (N) D1 D3 D5 D7Example 1 1.57 Absent absent present — Example 2 1.60 — — — — Example 31.79 — — — — Example 4 1.14 — — — — Example 5 1.09 absent absent absentabsent Example 6 1.02 — — — — Example 7 0.89 absent absent absent absentComparative 2.63 absent present present — Example 1 Comparative 2.44absent present present — Example 2 Comparative 2.54 — — — — Example 3Comparative 2.59 — — — — Example 4 Comparative 2.38 absent presentpresent — Example 5 Comparative 1.98 absent present present presentExample 6 Comparative 2.05 absent present present present Example 7Comparative 2.12 — — — — Example 8 Comparative 1.85 absent presentpresent present Example 9 Comparative 1.87 absent present presentpresent Example 10 Comparative 1.97 — — — — Example 11 blank 2.84 — — ——

From the results in Table 1, the samples of Examples 1 to 7 showed lowertape peeling force as compared with the samples of Comparative Examples1 to 11 and the blank sample. In particular, it was found that thesamples of Examples 4 to 7 had extremely low tape peeling force and theeffect remarkably appeared. From this, it was found that thecontamination-preventing agent composition of the present invention hasa pitch adhesion preventing effect.

Further, in the test on an actual machine, the samples of Examples 5 and7 manifested a sufficient contamination preventing effect even for adryer on the downstream side. On the other hand, any of the samples ofComparative Examples 5 to 7 and 9 and 10 were able to prevent the pitchcontamination of the dryer D1, but could not prevent the pitchcontamination of the downstream dryer.

INDUSTRIAL APPLICABILITY

The contamination-preventing agent composition of the present inventionis used by being imparted to a dryer in a dry part at the time of papermaking. According to the contamination-preventing agent composition ofthe present invention, it is possible to prevent pitch contamination ofa plurality of dryers as a whole, so that the yield in the production ofpaper can be greatly improved.

REFERENCE SIGNS LIST

-   -   1 . . . coating film,    -   1 a . . . emulsion,    -   10, 11 . . . dryer,    -   B . . . breaker stack roll,    -   C . . . calender roll,    -   D . . . dry part,    -   D1, D2, D3, D4, D5, D6, D7, D8 . . . dryer,    -   K1, K2 . . . canvas,    -   KR . . . canvas roll,    -   S1 . . . first step,    -   S2 . . . second step,    -   S3 . . . third step,    -   W . . . wet paper

1. A contamination-preventing agent composition imparted to a dryer in adry part of a paper machine and comprising an emulsion, a re-transferagent and water, wherein said re-transfer agent has a cloud point of 55°C. or higher and an HLB value of 8 to
 15. 2. Thecontamination-preventing agent composition according to claim 1, whereinthe dynamic surface tension value at a lifetime of 100 ms by a maximumbubble pressure method is 65 mN/m or less.
 3. Thecontamination-preventing agent composition according to claim 1, whereinsaid dryer is made of cast iron, and the contact angle to the cast ironis 70° or less.
 4. The contamination-preventing agent compositionaccording to claim 1, wherein said re-transfer agent is at least oneselected from the group consisting of polyoxyalkylene alkyl ether,polyoxyalkylene fatty acid ester, polyoxyalkylene sorbitan fatty acidester and polyoxyalkylene sorbitol fatty acid ester.
 5. Thecontamination-preventing agent composition according to claim 1, whereinsaid emulsion is composed of a non-silicone oil, water and anemulsifier, and said non-silicone oil is at least one selected from thegroup consisting of polybutenes, synthetic ester oils, mineral oils,vegetable oils and liquid paraffins.
 6. The contamination-preventingagent composition according to claim 5, wherein the compounding ratio ofsaid re-transfer agent with respect to 10% by mass of said non-siliconeoil is 0.1% by mass to 10% by mass.
 7. The contamination-preventingagent composition according to claim 1, wherein the compounding ratio ofsaid re-transfer agent is 0.01% by mass to 10% by mass.
 8. Thecontamination-preventing agent composition according to claim 1, whereina coating film is formed by being imparted to said dryer, and a part ofsaid coating film is re-emulsified when the coating film comes incontact with a wet paper.
 9. A contamination preventing method,comprising a first step of imparting the contamination-preventing agentcomposition according to claim 1 to a dryer on the upstream side to forma coating film, a second step of bringing a wet paper into contact withthe coating film to re-emulsify a part of the coating film and transferthe re-emulsified emulsion to the wet paper, and a third step ofbringing said wet paper carrying said emulsion into contact with a dryeron the downstream side to impart said emulsion to the dryer on thedownstream side.